Telephony generally refers to the use of equipment to provide voice communication over distances. Digital telephony uses digital features for telephone services and systems. Internet protocol (IP) telephony uses the Transmission Control Protocol/Internet Protocol (TCP/IP) to provide digitized voice data communications. Computer Telephony Integration (“CTI”) enables computers to make and receive voice, fax, and data calls which can also include telephone directory, voicemail, and caller identification (ID) services.